(1) Field of the Invention
This invention relates to an optical disc recording apparatus, a computer-readable recording medium recording a file management program, and an optical disc.
(2) Description of the Prior Art
Recently, recording mediums such as magneto optical discs (MO) have been widely used for recording data to be read by computers. Currently, practical uses of DVD (Digital Versatile Disc)-RAM discs are waited for due to general expectation that DVD-RAMs will become a main recording medium of the next generation.
In conventional MOs, like HD (Hard Disc) or FD (Flexible Disc), the minimum unit in accessing data on discs is “sector” having several kilobytes. Each file is recorded in one or more sectors.
Reading and writing of files from/onto discs are executed by computers as functions of a file system which is a part of operating systems (OS). A file system is defined, for example, in ISO/IEC13346.
According to a conventional technique, for example, when recording a file of 200 KB onto a recording medium with 2 KB-sectors, computers must find 100 unassigned sectors on the recording medium. The 100 unassigned sectors need not be physically consecutive. For example, when four separate groups respectively having 30, 30, 30, and 10 unassigned sectors are found on the recording medium, the file is divided into the four groups of sectors. Each part of the file recorded in each group of sectors, namely each group of consecutive sectors, is called “extent”.
In such a conventional technique, files can be divided and recorded into a plurality of extents. This provides a merit that all the sectors on a recording medium can be used efficiently even after recording and deleting of files on the medium are repeated a number of times.
However, conventional recording mediums and file systems have a problem that uninterrupted reproduction of audio/video data (hereinafter referred to as AV data) recorded on the recording mediums cannot be ensured.
More specifically, when recording and deleting of files on a recording medium are repeated several times, the AV data may not be recorded in consecutive sectors. The AV data may be divided and recorded into a plurality of extents, as described above. When this happens, the reproduction apparatus cannot achieve uninterrupted reproduction of the AV data due to a seek operation of an optical pickup that occurs as the optical pickup moves between the plurality of extents.
For example, when a seek occurs between-a sector at the innermost periphery and a sector at the outermost periphery of a disc, the seek time amounts to several-hundred milliseconds. In case of moving images, such a seek of several-hundred milliseconds interrupts reproduction since reproducing 30 frames per second is required for reproduction of moving images.
As described above, uninterrupted reproduction may not be ensured by conventional file systems. This is especially a serious problem for mass storages such as DVD-RAM on which, like VTR, a plurality of pieces of AV data (e.g., TV programs) can be recorded, edited, and deleted.
Here, it should be reminded that recording mediums can also record computer data, as well as AV data. Accordingly, particular attention should be paid on how to efficiently store both types of data on a disc.